1) Field
This disclosure relates to a fluid sensor, more particularly, to a fluid sensor for preventing air bubble generation when sensing the fluid, thereby increasing the fluid sensor's sensitivity.
2) Description of the Related Art
A sensor is a device that responds to a stimulus and correspondingly emits an impulse signal, which can be subsequently read by an observer or an instrument. Some sensors are used for sensing and measuring active materials or physical changes resulting from the reaction of a target material upon contact with an electrical, a physical or a chemical device. One type of such a sensor is a fluid sensor, which senses for presence of a certain target material in a fluid. An example of a fluid sensor is a biosensor, which detects the presence of a target material in a bio sample by immobilizing, on a certain substrate, a receptor material that specifically binds to the target material. Subsequently, the bio sample containing the target material flows on the surface of the sensor, which outputs a signal for reading by an observer or an instrument.
Mass sensors, which typically measure a change in a sensor surface mass, are sensitive to fluid pressure and viscosity and density of a medium. For example, when the sensed sample is a solution, the mass sensor is highly affected by the solution's pressure, viscosity and density, resulting in generation of a noise, which is greater than a sensing signal. Hence, the mass sensor cannot be properly operated. Particularly, due to the structure of a current sensing chamber in a mass sensor, air bubbles are often generated in the solution, leading to changes in the sensor surface pressure and the viscosity and density of the solution. The signal noise resulting from air bubble generation thus prevents the mass sensor from functioning properly.